The teachings herein relate generally to a method for correcting error in nacelle measured wind speed for a wind driven turbine.
Wind driven turbines are increasingly relied upon to help alleviate society's increasing demand for energy. Accordingly, sophisticated techniques are called for to ensure reliable operation and optimum performance of each wind turbine in service. Thus, accurate assessments of wind speed are desired to help address the demand for energy.
One technique for making accurate assessments of wind speed involves the use of a separate meteorological mast. This technique calls for placing a separate tower adorned with measurement equipment (for example, an anemometer) some distance upwind of the wind turbine. Although this technique can provide accurate assessments of wind speed, this technique is economically expensive. Further, this technique may not provide the desired accuracy in some cases, such as in complex terrain.
Another technique involves placing an anemometer on the nacelle of the wind driven turbine. Comparison of wind speed measurements taken with a nacelle based anemometer shows that the nacelle based wind speed measurements do not accurately correlate to those measurements taken with equipment upon a meteorological mast. Investigation of this problem has revealed that wind speed measurements taken with a nacelle-based anemometer are influenced by the power production of the wind turbine for any given wind speed. In effect, the indication of wind speed is coupled to the power produced. Unfortunately, existing data acquisition systems assume proportionality between measurements taken with a nacelle-based anemometer and the free stream wind speed. Such systems do not properly account for error, and as a result, application of wind speed data for various operations is not as accurate as can be realized. Accordingly, operations such as turbine optimization are not as effective as possible.
For many reasons, accurate measurements of the free stream wind speed are desired. For example, improved measurements will result in reduced variance and risk in a power curve test. Reduction in or elimination of requirements for site calibration can be realized, thus reducing cost and time expenditures. This can further benefit operators by reducing or eliminating the need for flow correction associated with most terrain variations. Further benefits include, without limitation, improved system optimization, as well as improved accuracy for load planning and performance evaluation.
What is needed is a method to accurately determine ambient wind speed from nacelle based measurement equipment.